1. Field of the Invention
The present invention relates generally to low energy mechanical switches. The invention relates more specifically to contact designs for those switches.
2. Description of Prior Art
Mechanical switching at low energy, i.e. transferring low currents at low voltages, for example to avoid sparking, is often problematic. Low current is generally meant to include the range of 0.001 to 0.050 amp. The low current does not provide sufficient energy, or spark, at the contacts to burn away contaminants thereon.
Contaminant build up will occur unless physical cleaning of the contact point takes place during the time the moveable contact comes into contact with the stationary contact. This physical cleaning is called wiping. Also, troughing of the contact point, wherein a groove is formed in the mating surfaces, may occur on one or both contact surfaces. Troughing causes loss of wiping action when the movable contact makes contact with the stationary contact. Loss of wiping means contaminants will not be moved away from the contact area, resulting in less efficient current flow. Troughing also changes switch mechanics, causing operate point variability and, at the extreme, can result in mechanical interlock and loss of switch function.
Therefore, it would be desirable to have a switch design which can retain good electrical contact characteristics while operating at low energies.